1. Field of the Invention
The present invention relates to an electrophotographic information recording medium comprising forming (recording) an image directly thereon by using an electrophotographic system image forming device. The present invention relates particularly to a non-contact or contact type information recording medium containing private information and image information such as a cash card, employee identification card, student identification card, individual membership card, residence certificate, various driver's licenses and various qualification certificates that contain a photograph of a holder's face, and further, to an electrophotographic information recording medium used for a personal identification image sheet and image display board and a display label used in medical sites and the like. The present invention also encompasses a method of producing these information recording media.
2. Description of the Related Art
Along with the development of recent image forming technologies, measures taken to form images having the same qualities in a large amount at low cost by using various printing methods such as intaglio printing, relief-printing, planographic printing, gravure printing and screen printing have been known. Many such printing methods are used for surface printing of information recording media, such as IC cards, magnetic cards, optical cards or cards composed of combinations of these cards, which store predetermined information and can communicate with external devices in a contact or non-contact system.
However, for example, the screen printing requires many printing plates corresponding to the number of images which it is intended to print. In the case of color printing, printing plates in accordance with the number of the colors are further required. For this reason, these printing methods are not suitable for printing personal identification information (e.g., photographs of the face, name, residence, date of one's birth and various kinds of licenses).
In light of the above problems, currently most major image forming methods employ printers and the like utilizing a sublimation type or melt type thermal transfer system using an ink ribbon or the like. These methods enable personal identification information to be printed with ease. However, these image forming methods still have a problem that resolution deteriorates when increasing printing speed whereas printing speed decreases when raising resolution.
In the meantime, image forming (printing) using an electrophotographic system is accomplished by the following process: the surface of a latent image holding member is charged evenly, exposed to light corresponding to image signals to form an electrostatic latent image by the potential difference between the exposed part and the unexposed part, and then a color powder (image forming material), called a toner, having polarity opposite (or the same) to (as) that of the above charge is subjected to electrostatic developing to thereby form a visible image (toner image) on the surface of the latent image holding member. In the case of a color image, image forming is accomplished using a method in which the above step is repeated or plural image forming devices are arranged in parallel to thereby form a color visible image, which is then transferred and fixed (fixation: solidification of the color powder by melting using heat and cooling) to an image recording material to thereby obtain a color image.
In the electrophotographic system as described above, the electrostatic latent image on the surface of the latent image holding member is electrically formed by image signals. Therefore, not only the same image can be formed repeatedly but also it is possible to cope with different images with ease to form an image. A toner image formed on the latent image holding member can be transferred almost perfectly to the surface of the image recording material and also a little toner image left on the surface of the latent image holding member can be easily removed using a resin blade or a brush. By using the electrophotographic system it is easy to produce print products appropriate for multi-product low-volume production.
Also, the aforementioned toner is usually formed by melting and mixing a heat-meltable resin, a pigment and, when necessary, additives such as a charge regulator and crushing the kneaded product to micronize. Furthermore, the electrostatic latent image in the above electrophotographic system has considerably higher resolution than the aforementioned micronized toner. It can be expected to obtain sufficient resolution compared with that obtained in the aforementioned screen printing or the aforementioned thermal transfer system using an ink ribbon.
With respect to a color image, four primary colors, namely cyan, magenta, yellow and black, are used for color toners and color toners having these colors are mixed whereby the same color as in the case of printing can be theoretically reproduced. Also, in the case of the above color toner, it is easy to increase image-masking ability by means of a toner because a toner resin and a pigment can be compounded relatively freely.
Little study has been made yet as to heat resistance and light resistance on the assumption of outdoor use. Particularly when driver's license and the like are left on a place exposed to the direct rays of the sun in a car, an image in thermal transfer system using a dye as a colorant is faded. However, in a color image output in an electrophotographic system, pigments superior in light resistance corresponding to each color of cyan, magenta, yellow and black are used. It is therefore considered that the image recording material in an electrophotographic system has satisfactorily superior light resistance. Similarly, the heat resistance of the image recording material is considered to be improved to a level at which the image recording material can be used outdoors.
The core base material for various kinds of cards used most frequently at present is a vinyl chloride sheet. This is because the vinyl chloride sheet is superior in printing characteristics and also in adaptability to embossing processing (processing of irregularities such as characters). However, the vinyl chloride sheet has a problem that it generates dioxins when incinerated in a furnace and the like for waste disposal resulting from, for example, the expiration of the time limit. Therefore, various sheet films are used at present as materials excluding the vinyl chloride from the viewpoint of coping with the environment.
In a case where embossing processing is not to be applied, a conventional biaxial oriented PET (polyethylene terephthalate) film and the like may be used. However, embossing processing is essential in many cases to retain the functions of conventional cards. At present, therefore, ABS films and polyolefin resin films which are softened at relatively low temperatures, modified PET resin films called PETG and integrally formed films of a modified PET film and a PET film, an amorphous PET resin film or a polycarbonate resin film come to be used.
The following examples are given as examples using the aforementioned electrophotographic device to carry out printing of various cards.
Japanese Patent Application Laid-Open (JP-A) No. 11-334265 proposes a method in which personal identification information is printed on a light-transmittable sheet and further, printed as a mirror image, which is then applied to the surface of a base material having an IC memory to make a card.
As a method of producing cards including IC cards, a method is known in which an image is formed on a plastic sheet and then applied to or laminated on a card base material (see, for example, JP-A Nos. 7-266723 and 2001-92255). Also, a method is generally known in which a print surface obtained by printing an image as a mirror image on a light-transmittable sheet is laminated on a card base material or a foil substrate to make cards or display media (see, for example, JP-A Nos. 10-86562 and 7-89209).
In the aforementioned method of producing a card by using the electrophotographic system, the surface resistance of each transfer film is not defined and the above-exemplified polyester, ABS, and vinyl chloride type film is usually an insulating body. When such an insulating body is used as an electrophotographic transfer film, a toner-transfer defect may be caused. Moreover, the electrostatic adsorption power of a transfer film after the transfer process and fixing process of a toner image becomes excessively large, resulting in that a transfer film is easily adhered with another transfer film or with a base material, to which the transfer film is to be laminated, at undesirable portions.
For this reason, it is sometimes difficult to align the transfer film with the base material at a desired position to laminate by an automatic operation, for instance, to align a personal identification information image with a corresponding IC memory exactly. It is, thus, necessary to make alignment by a hand operation, posing the problem that a laminate position is inexact and working efficiency is significantly decreased. There has also been a problem that dirt such as dusts is easily adsorbed by static electrification and therefore the finish quality of cards is deteriorated.